JP5917940B2 - Surface lighting device - Google Patents

Description

  The present invention relates to a planar illumination device used as illumination means such as a liquid crystal display device.

  Nowadays, liquid crystal display devices are generally used as display devices for electronic devices such as personal computers and mobile phones. Since liquid crystal is not a self-luminous display element, for example, in a transmissive liquid crystal display device, illumination means for irradiating light to the liquid crystal panel is essential, and a transflective liquid crystal display device using external light However, auxiliary lighting means are provided to enable use in the dark. As an illuminating means of such a liquid crystal display device, a planar illuminating device having a light guide plate and a light source disposed on the side of the light guide plate as main components has an advantage that it can be easily reduced in thickness. Therefore, it is widely used in combination with a liquid crystal display device. In addition, with the recent improvement in performance of white light emitting diodes (LEDs), a planar lighting device using a white LED as a light source is generally used in order to further reduce the size and thickness of the planar lighting device and reduce power consumption. It has become.

  An example of a display device provided with such a planar illumination device is shown in FIG. In FIG. 6, the display device 100 includes a liquid crystal display panel (LCD) 110 including a pair of glass substrates 112 and a polarizing plate 114, and one (front surface) of a pair of opposing main surfaces disposed on the back side of the LCD 110. A light guide plate 116 serving as a light output surface, a reflection sheet 118 disposed on the back side of the light guide plate 116, and a plurality of layers (four layers in the example of FIG. 6) disposed between the LCD 110 and the light guide plate 116. A plurality of plate-like (or sheet-like) members such as the sheet 120 are included as constituent elements. And these structural elements are frame shape of the frame 124 which consists of synthetic resin materials with the point light sources 122, such as white LED arrange | positioned facing the light-incidence surface 116a (FIG.6 (c)) of the light-guide plate 116. FIG. It is stored inside and configured as an integrated display device 100.

In the display device 100 having such a configuration, the LCD 110 is fixed to a mounting seat 124a formed so as to protrude inside the frame 124 via a double-sided tape 126 (FIG. 6B). . The optical sheet 120 includes, for example, a diffusion sheet, a prism sheet, and the like, and is fixed to the mounting seat 124 a of the frame 124 via the double-sided tape 126, as with the LCD 100. Further, the reflection sheet 118 is also fixed by a double-sided tape 127 to a mounting seat 124 b formed so as to protrude inside the frame 124. Further, a light shielding member 128 that covers the point light source 122 and the light incident surface 116a (FIG. 6C) of the light guide plate 116 is disposed. In addition, the code | symbol 130 in FIG.6 (c) is a double-sided tape, and the code | symbol 132 is a wiring board of a point light source. (For example, refer to Patent Document 1).
Further, in order to ensure the positioning of the optical sheet 120, tabs 120a as shown in FIG. 5A are formed on the end sides of the optical sheet 120, and tabs 120a are formed at corresponding positions of the frame 124. A recess 124c having a complementary shape for receiving the recess is formed. Therefore, the optical sheet 120 is positioned with respect to the frame 124 in the directions of arrows A and B orthogonal to each other as shown in FIG. 5A (see, for example, Patent Documents 2 and 3). .

JP 2010-224000 A JP 2009-265237 A JP 2006-154320 A

As described above, the display device 100 has a structure in which necessary components are integrally held and necessary strength is secured by the frame 124 arranged so as to surround the LCD 110 in a frame shape. By the way, not only from the viewpoint of functionality such as miniaturization of the display device 100 but also from the viewpoint of design, a narrow frame for the display device 100 is always required. In order to promote this narrowing of the frame, when the thickness of the frame 124 (thickness in the direction of arrow B in FIG. 5A) is reduced, a recess 124c for receiving the tab 120a of the optical sheet 120 is secured. It becomes difficult. And since there exists a possibility that the positioning of the optical sheet 120 may become inadequate, it is an obstacle in satisfy | filling the request | requirement of the narrow frame of the display apparatus 100. FIG. In addition, the tab 120 a of the optical sheet 120 can be a cause of luminance unevenness of the planar lighting device constituting the display device 100.
The present invention has been made in view of the above problems, and the object of the present invention is to make it possible to reliably position the optical sheet in the planar illumination device without forming a tab on the optical sheet, It is to promote further narrowing of the frame lighting device. Another object of the present invention is to suppress the occurrence of uneven brightness in the planar lighting device due to the tab of the optical sheet.

(Aspect of the Invention)
The following aspects of the present invention exemplify the configuration of the present invention, and will be described separately for easy understanding of various configurations of the present invention. Each section does not limit the technical scope of the present invention, and some of the components of each section are replaced, deleted, or further while referring to the best mode for carrying out the invention. Those to which the above components are added can also be included in the technical scope of the present invention.

(1) A light guide plate having one of a pair of opposing main surfaces as a light exit surface, a plurality of optical sheets stacked on the exit surface, a light shielding member that defines an effective area of the exit surface, A planar illumination device including a light source disposed to face a light incident surface of a light guide plate and a frame for housing these components, wherein the plurality of optical sheets are counted from the light exit surface. The optical sheet with the upper laminated layer is formed such that the position of the edge on the light incident surface side of the light guide plate is separated from the light incident surface of the light guide plate, and the light shielding member is the light guide plate. A planar illumination device that extends from the light incident surface side of each of the plurality of optical sheets so as to cover the vicinity of each edge portion without forming steep bent portions and is fixed to the optical sheets (claims). 1).
In the planar illumination device described in this section, among the plurality of optical sheets, the position of the edge portion on the light incident surface side of the light guide plate is the position of the light guide plate on the upper side of the optical sheet that is stacked from the emission surface. By being formed so as to be separated from the light incident surface, the edge of the light guide plate on the light incident surface side of each optical sheet is positioned in the upper stage in a mode in which the light exit surface of the light guide plate is viewed in plan view. It is exposed without being covered by the optical sheet. A steep bent portion is formed on the exposed edge portion of each optical sheet so that the light shielding member covers the vicinity of each edge portion of the plurality of optical sheets from the light incident surface side of the light guide plate. By extending without any problem, the exposed portions near the edge portions of all the optical sheets are fixed by the light shielding member. For example, a double-sided tape or an adhesive is used for fixing the light shielding member to each optical sheet.

(2) In the above item (1), the thickness between the opposed main surfaces is set to the central portion of the light guide plate within a predetermined width range near the central portion from the light incident surface of the light exit surface of the light guide plate. An inclined surface that is thinner toward the center is formed, the range closer to the center than the inclined surface has a constant thickness, and from the edge of the light guide plate on the light incident surface side of the plurality of optical sheets A planar illumination device in which a range of a predetermined width is inclined following an inclined surface formed on an emission surface of the light guide plate (Claim 2).
In the planar illumination device described in this section, the range of a predetermined width from the edge of the light guide plate on the light incident surface side of the plurality of optical sheets is inclined following the inclined surface formed on the light exit surface of the light guide plate. By doing so, the light shielding member extending from the light incident surface side of the light guide plate so as to cover the vicinity of each edge portion of the plurality of optical sheets is fixed along the inclined surface of each optical sheet. This also prevents a steep bent portion from being formed on the light shielding member extending from the light incident surface side of the light guide plate, and sufficiently secures the fixing strength of the light shielding member to each optical sheet.

(3) In the above item (2), the light source is disposed between the inclined surface of the light guide plate and the optical sheet in which the stacked layers counted from the light exit surface among the plurality of optical sheets are positioned at the lowest level. A planar illumination device in which the wiring boards are laminated (claim 3).
The planar illumination device described in this section is configured such that the light guide plate also includes a light source wiring substrate that is laminated between the inclined surface of the light guide plate and the optical sheet in which the laminated steps counted from the emission surface are positioned at the lowest level. This prevents a steep bent portion from being formed on the light shielding member extending from the light incident surface side and sufficiently secures the fixing strength of the light shielding member to each optical sheet.
( 4 ) In the above item (2) (3) , among the plurality of optical sheets, the optical sheet in which the stacking stage counted from the exit surface is located at the uppermost stage is arranged on the inclined surface of the optical sheet located in the lower stage. A planar illumination device that is arranged in parallel with the light exit surface of the portion having a certain thickness of the light guide plate without being hung (Claim 4 ).
In the planar illumination device described in this section, the optical sheet in which the stacking step counted from the exit surface is positioned at the uppermost stage is arranged in parallel with the exit surface of the constant thickness portion of the light guide plate. The vicinity of the front end portion of the light shielding member extending so as to cover the vicinity of each edge portion of the plurality of optical sheets from the light incident surface side of the light plate is also parallel to the light exit surface of the light guide plate on the optical sheet located at the uppermost stage. Will be placed. Then, the object to be illuminated is stabilized by mounting an object to be illuminated such as a polarizing film of an LCD on the surface of the light shielding member parallel to the exit surface of the light guide plate.

( 5 ) In the above item ( 4 ), among the plurality of optical sheets, the guide of the optical sheet positioned on the uppermost surface of the optical sheet, the optical sheet positioned immediately below the uppermost layer being counted from the emission surface, is provided. A planar illuminating device in which positions in the stacking direction of the plurality of optical sheets coincide with or substantially coincide with the upper edge of the edge on the light incident surface side of the optical plate (Claim 5 ).
The planar illuminating device described in this section includes an optical surface between the upper surface of the optical sheet positioned at the uppermost stage and the upper edge of the edge of the light guide plate on the light incident surface side of the optical sheet positioned immediately below the optical sheet. When the positions in the sheet stacking direction match or substantially match, the position in the vicinity of the tip of the light shielding member in the optical sheet stacking direction is arranged in parallel with the exit surface of the light guide plate. . That is, the vicinity of the tip of the light shielding member is related not only to the upper surface of the optical sheet positioned at the uppermost stage but also to the upper edge of the edge of the optical sheet positioned immediately below the optical sheet in the stacking direction of the optical sheets. By being supported in a manner in which the positions match or substantially match, the vicinity of the tip of the light shielding member is stably supported over a wider range and parallel to the exit surface of the light guide plate. In this description, the term “substantially coincidence” is intended to allow inconsistencies within an allowable range from the viewpoint of dimensional accuracy and assembly accuracy of each component.

( 6 ) In the above items (2) to ( 5 ), of the plurality of optical sheets, an end of the optical sheet on the light incident surface side of the light guide plate in which the stacking step counted from the exit surface is positioned at the lowest step The position related to the stacking direction of the plurality of optical sheets on the upper edge of the edge on the light incident surface side of the light guide plate of the optical sheet located immediately above the upper edge of the edge is downward. The planar lighting device located (Claim 6 ).
The planar illumination device described in this section is positioned immediately above the upper edge of the edge on the light incident surface side of the light guide plate of the optical sheet in which the stacking step counted from the exit surface is located at the lowest step. The position of the upper edge of the edge of the light guide plate on the light incident surface side of the optical sheet that is related to the stacking direction of the plurality of optical sheets is located below, so that the light guide plate can be viewed from the light incident surface side of the light guide plate. The light shielding member extending so as to cover the vicinity of each edge portion of the plurality of optical sheets constitutes an inclined surface following the inclined surface of the optical sheet in which the stacking steps counted from the emission surface are positioned at the lowest level. Then, the inclined surface of the light shielding member is maintained from the optical sheet positioned at the lowest level to the position where the light shielding member rides over the optical sheet positioned immediately above it. This also prevents a steep bent portion from being formed on the light shielding member, and sufficiently secures the fixing strength of the light shielding member with respect to each optical sheet.

( 7 ) In the above items (1) to ( 6 ), the plurality of optical sheets are stacked on the first sheet, the first sheet having the first stacked layer counted from the exit surface of the light guide plate. A planar lighting device including a second sheet and a third sheet laminated on the second sheet (Claim 7 ).
In the planar illumination device described in this section, the plurality of optical sheets stacked and arranged on the light exit surface of the light guide plate includes a first sheet, a second sheet, and a third sheet. To ( 6 ).
(8) In the above items (1) to (7), a planar illumination device in which front and back and upper and lower discriminating means are provided on the edge of the light guide plate on the light incident surface side of the plurality of optical sheets. (Claim 8).
In the planar illumination device described in this section, in the state before the light shielding member covers the vicinity of the edge portions of the plurality of optical sheets from the light incident surface side of the light guide plate, the light incident on the light guide plate of each optical sheet The front / back and upper / lower discriminating means provided at the edge portion on the surface side are exposed without being covered by the optical sheet located on the upper stage in a mode in which the emission surface of the light guide plate is viewed in plan. For this reason, it is possible to determine at a glance whether the plurality of optical sheets are front and back and up and down in a state before the light shielding member covers the vicinity of each edge portion of the plurality of optical sheets from the light incident surface side of the light guide plate. It will be possible.

( 9 ) A light guide plate having one of a pair of opposing main surfaces as a light exit surface, a plurality of optical sheets stacked on the exit surface, a light shielding member that defines an effective area of the exit surface, A method of fixing the optical sheet of a planar illumination device including a light source disposed opposite to a light incident surface of a light guide plate and a frame for housing these components, the plurality of optical sheets Is formed such that the position of the edge portion on the light incident surface side of the light guide plate is separated from the light incident surface of the light guide plate, as the optical sheet with the uppermost laminated stage counted from the light exit surface, and The light shielding member is extended from the light incident surface side of the light guide plate so as to cover the vicinity of each edge portion of the plurality of optical sheets without forming steep bent portions, and is fixed to each optical sheet. Method.
( 10 ) In the above item ( 9 ), the thickness between the pair of opposing main surfaces is set to a central portion of the light guide plate in a range of a predetermined width near the central portion from the light incident surface of the output surface of the light guide plate. An inclined surface that is thinner toward the center is formed, a range closer to the center than the inclined surface is set to a constant thickness, and a range of a predetermined width from an edge of the light guide plate on the light incident surface side of the plurality of optical sheets A fixing method in which the light is inclined following the inclined surface formed on the light exit surface of the light guide plate.

(11) In the above item (9), the light source is disposed between the inclined surface of the light guide plate and the optical sheet in which the stacked layers counted from the emission surface are positioned at the bottom of the plurality of optical sheets. Method of stacking multiple wiring boards.
( 12 ) In the above item ( 10 ) (11) , among the plurality of optical sheets, the optical sheet in which the stacking stage counted from the emission surface is located at the uppermost stage is on the inclined surface of the optical sheet located in the lower stage. The fixing method which arrange | positions in parallel with the output surface of the part of the fixed thickness of the said light-guide plate, without hanging.
( 13 ) In the above item ( 12 ), among the plurality of optical sheets, the guiding of the upper surface of the optical sheet in which the stacking level counted from the emission surface is located at the uppermost stage and the optical sheet located immediately below the uppermost stage. The fixing method which makes the position which concerns on the lamination direction of the said some optical sheet correspond with the upper edge of the edge part by the side of the light-incidence surface of an optical plate correspond to or substantially correspond.

( 14 ) In the above items ( 9 ) to ( 13 ), of the plurality of optical sheets, an end of the optical sheet on the light incident surface side of the light guide plate in which the stacked stage counted from the exit surface is located at the lowest stage With respect to the upper edge of the edge portion, the position of the optical sheet located immediately above the upper edge of the edge portion on the light incident surface side of the light guide plate in the stacking direction of the plurality of optical sheets is downward. Fixing method to place.
( 15 ) In the above paragraphs ( 9 ) to ( 14 ), the plurality of optical sheets are stacked on the first sheet with the first sheet having the first stacked layer counted from the light exit surface of the light guide plate. A fixing method including two sheets and a third sheet laminated on the second sheet.
(16) The fixing method according to (9) to (15) above, wherein front and back and upper and lower discriminating means are provided at the edge of the light guide plate on the light incident surface side of the plurality of optical sheets.
And according to the fixing method of an optical sheet as described in said ( 9 ) to ( 16 ) term, there exists an effect | action corresponding to the planar illuminating device of said (1) to ( 8 ) term, respectively.

  Since the present invention is configured as described above, it is possible to reliably position the optical sheet in the planar illumination device without forming a tab on the optical sheet, and to promote further narrowing of the planar illumination device. It becomes possible to do. In addition, it is possible to suppress the occurrence of luminance unevenness of the planar illumination device due to the tab of the optical sheet.

It is sectional drawing which shows the planar illuminating device which concerns on embodiment of this invention. It is a principal part perspective view of the planar illuminating device shown by FIG. 1, (a) shows the state before sticking a light shielding sheet to an optical sheet, (b) shows the state after sticking. It is a principal part perspective view which shows the example of application to the planar illuminating device which has a sheet-metal frame. It is a perspective view which shows the front and back of an optical sheet, and the upper and lower discrimination means. It is a perspective view which shows the flame | frame and optical sheet | seat of a planar illuminating device, (a) is what used the optical sheet which has the conventional tab as a reference example, (b) is embodiment of this invention, It is shown. FIG. 1 shows a liquid crystal display device including a conventional planar illumination device, where (a) is a plan view, (b) is a sectional view taken along line DD in (a), and (c) is a sectional view taken along line EE in (a). FIG.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In addition, about the same part as a prior art, or a part corresponding, the same code | symbol is attached | subjected suitably and detailed description is abbreviate | omitted. Further, the directions of “up” and “down” in the following description mean the vertical direction in the state where the planar lighting device in the present description is placed flat.

1 to 3 show a planar illumination device 10 according to an embodiment of the present invention. The planar illumination device 10 includes a light guide plate 12 having one of a pair of opposing main surfaces 12a and 12b as a light output surface, a plurality of optical sheets 18 arranged in a stacked manner on the output surface 12a, and an output. A light shielding member 20 that defines an effective area of the surface 12a, an LED (which is a point light source) disposed as opposed to the light incident surface 12c of the light guide plate 12, and a component for housing these components And a frame 16 made of synthetic resin. By the way, the “effective area” of the emission surface 12 a defined by the light shielding member 20 is affected by the reflection of light on the side end surface of the light guide plate 12 and the uniformity of the emitted light is reduced. This is an area excluding the “ineffective area” that inevitably occurs in the vicinity of the edge of the emission surface 12a. In the planar illumination device described in this section, the non-effective area is covered with the light shielding member 20 in a plan view of the emission surface 12a of the light guide plate 12, and the emitted light from the effective area is used to the maximum extent possible. For example, a light shielding sheet is used for the light shielding member 20.
In addition, the part shown with the code | symbol 16b in FIG. 1 is a mounting seat for positioning the reflective sheet 118, and using this double-sided tape 127 (refer FIG.6 (b)) with respect to this mounting seat 16b, A reflective tape 118 is fixed.

  In the present embodiment, the optical sheet 18 includes a first sheet 181 in which the number of layers counted from the light exit surface 12a of the light guide plate 12 is the first sheet 181 and a second sheet 182 stacked on the first sheet 181. And a third sheet 183 stacked on the second sheet 182. As an example, the first sheet 181 is a diffusion sheet, the second sheet 182 is a lower prism sheet, and the third sheet 183 is an upper prism sheet. The optical sheets 181, 182, and 183 are configured so that end edges 181 b, 182 b, and 183 b of the light guide plate 12 on the side facing the light incident surface 12 c (refer to FIG. 1) are the inner periphery of the frame 16. When the optical sheet is in the state of being in contact with the surface and being aligned in plan view, the optical sheet having the uppermost laminated stage counted from the emission surface 12a of the light guide plate 12, the edge portions 181a and 182a on the light incident surface 12c side of the light guide plate 12 are arranged. , 183a is formed so as to be separated from the light incident surface 12c of the light guide plate 12.

  Then, the light shielding member 20 extends from the light incident surface 12c side of the light guide plate 12 in the vicinity of the edge portions 181a, 182a, 183a of the optical sheets 181, 182, 183 on the light incident surface 12c side of the light guide plate 12. It extends to cover. The light shielding member 20 is, for example, a double-sided tape 130 (see FIG. 2) with respect to the vicinity of the edge portions 181a, 182a, 183a of the optical sheets 181, 182, 183 on the light incident surface 12c side of the light guide plate 12. ) Or bonding.

In addition, in the range of a predetermined width of the light exit surface 12a of the light guide plate 12 closer to the center portion from the light incident surface 12c, an inclined surface 12d that reduces the thickness between a pair of opposing main surfaces toward the center portion of the light guide plate. The range closer to the center than the inclined surface 12d has a constant thickness.
Of the optical sheets 181, 182, and 183, the first sheet 181 and the second sheet 182 have a predetermined width range from the edge portions 181 a and 182 a on the light incident surface 12 c side of the light guide plate 12. It is inclined following the inclined surface 12d formed on the emission surface 12a.

In the example shown in FIG. 1, the wiring board 132 of the light source 14 is inclined along the inclined surface 12d of the light guide plate 12, and is fixed to the inclined surface 12d with a double-sided tape 130. Then, by laminating the first sheet 181 on the wiring board 132, a range of a predetermined width from the end edge 181a on the light incident surface 12c side of the light guide plate 12 follows the inclined surface 12d of the light guide plate 12. It is inclined. In addition, the second sheet 182 is laminated on an inclined portion having a predetermined width from the edge 181a on the light incident surface 12c side of the light guide plate 12 of the first sheet 181, so that the light incident surface of the light guide plate 12 is laminated. A range of a predetermined width from the end edge 182a on the 12c side is also inclined following the inclined surface 12d of the light guide plate 12. The “predetermined width range” is determined by the positional relationship between the inclined surface 12 d of the light guide plate 12 and the edge portions 181 a and 182 a of the sheets 181 and 182.
On the other hand, the third sheet 183 in which the stacking stage counted from the light exit surface 12a of the light guide plate 12 is positioned at the uppermost stage does not reach the inclined surface of the second sheet 182 positioned immediately below the third sheet 183, and the light guide plate 12 is fixed. Are arranged in parallel with the exit surface 12a of the thickness portion.

Also, as shown in FIG. 1, among the optical sheets 181, 182, and 183, the upper surface 183c of the third sheet 183 in which the stacking stage counted from the exit surface 12a of the light guide plate 12 is positioned at the uppermost stage, and immediately there The position (vertical direction position) in the stacking direction of the optical sheet 18 with the upper edge 182e of the edge 182a on the light incident surface 12c side of the light guide plate 12 of the second sheet 182 positioned in the lower stage is not coincident. It is almost coincident.
Further, among the optical sheets 181, 182, and 183, the edge portion on the light incident surface side 12 c of the light guide plate 12 of the first sheet 181 in which the stacking level counted from the light exit surface 12 a of the light guide plate 12 is located at the lowest level. The position of the upper edge 182e of the edge 182a on the light incident surface 12c side of the light guide plate 12 of the second sheet 182 positioned immediately above the upper edge 181e of 181a in the stacking direction of the optical sheet 18 ( (Position in the vertical direction) is located below.

  FIG. 3 shows an example in which the frame 16 made of the synthetic resin shown in FIG. 1 is replaced with a sheet metal frame 22 as an application example of the present invention. Also in this application example, the light guide plate 12, the optical sheets 181, 182, 183, and the light shielding member 20 have the same configuration as the example of FIGS. 1 and 2. Since the frame is the sheet metal frame 16, the frame itself has greater strength than the resin frame. Although not shown in FIG. 3, the metal plate frame 22 is provided with protrusions for positioning the respective components in the side surface direction orthogonal to the light incident surface 12 c of the light guide plate 12 as necessary. Also good.

  Further, as illustrated in FIG. 4, for example, as illustrated in FIG. 4, as the front / back and upper / lower discriminating means of each optical sheet, for example, an edge 181 a on the light incident surface side of the light guide plate of the first and second sheets. , 182a may be provided with C surface portions 181c and 182c, and a tab 183d may be provided at an asymmetrical position in plan view on the edge portion 183a of the third sheet 183 on the light incident surface side of the light guide plate.

Now, according to the embodiment of the present invention configured as described above, the following operational effects can be obtained.
That is, in the embodiment of the present invention, the positions of the edge portions 181 a, 182 a, 183 a on the light incident surface 12 c side of the light guide plate 12 of the plurality of optical sheets 181, 182, 183 are the exit surfaces 12 a of the light guide plate 12. Each optical sheet 181 is formed in such a manner that the emission surface 12a of the light guide plate 12 is viewed in plan view by being formed so that the upper-stage optical sheet is separated from the light incident surface 12c of the light guide plate 12 as the upper optical sheet is counted. The edge portions 181a, 182a, 183a of the light guide plate 12 on the light incident surface 12c side of 182 and 183 are exposed without being covered by the optical sheets located on the upper stages. The light shielding member 20 is attached to the exposed edge portions 181a, 182a, 183a of the optical sheets 181, 182, 183 from the light incident surface 12c side of the light guide plate 12, and the edge portions 181a of the plurality of optical sheets 18 are provided. By extending so as to cover the vicinity of 182a and 183a, the vicinity of the edge portions 181a, 182a and 183a of all the optical sheets 181, 182 and 183 is fixed by the light shielding member 20.

In addition, a range of a predetermined width from the end edge portions 181 a and 182 a on the light incident surface 12 c side of the light guide plate 12 of the plurality of optical sheets 181 and 182 follows the inclined surface 12 d formed on the light exit surface 12 a of the light guide plate 12. As a result of the inclination , steep bent portions are formed so as to cover the vicinity of the edge portions 181a, 182a, 183a of the plurality of optical sheets 181, 182, 183 from the light incident surface 12c side of the light guide plate 12. The light shielding member 20 that extends without being fixed is fixed along the inclined surfaces of the optical sheets 181 and 182. Thus, the light blocking member 20 extending from the light entrance surface 12c side of the light guide plate 12, that extend without sharp bending portion is formed, the fixing strength of the light shielding member 20 for each optical sheet 181, 182, 183 It is possible to ensure sufficient.

In addition, the optical sheet 183 having the uppermost laminated layer counted from the light exit surface 12a of the light guide plate 12 is arranged in parallel with the light exit surface 12a of the constant thickness portion of the light guide plate 12, so that the light guide plate The vicinity of the front end portion 20a of the light shielding member 20 extending so as to cover the vicinity of the end edge portions 181a, 182a, 183a of the plurality of optical sheets 181, 182, 183 from the 12 light incident surface 12 c side is also located at the uppermost stage. On the optical sheet 183, it will be arrange | positioned in parallel with the output surface 12a of the light-guide plate 12. FIG. Then, an object to be illuminated such as an LCD polarizing film (see LCD 110, pair of glass substrates 112 and polarizing plate 114 in FIG. 6) is mounted on the surface of the light shielding member 20 parallel to the exit surface 12a of the light guide plate 12. This makes it possible to stabilize the illuminated object.
In addition, the light guide plate 12 is also inserted by the wiring board 132 of the light source 14 laminated between the inclined surface 12d of the light guide plate 12 and the optical sheet 181 in which the laminated steps counted from the emission surface 12a are located at the lowest level. It is possible to prevent a steep bent portion from being formed on the light shielding member 20 extending from the light surface 12c side, and to sufficiently secure the fixing strength of the light shielding member 20 to the optical sheets 181, 182, and 183.

  In the embodiment of the present invention, the edge 182a of the light guide plate 12 on the light incident surface 12c side of the upper surface 183c of the third sheet 183 positioned at the uppermost stage and the second sheet 182 positioned immediately below the upper surface 183c. The position of the upper edge 182e with respect to the stacking direction (vertical direction) of the optical sheet 18 matches or substantially matches. As a result, the position in the vicinity of the distal end portion 20 a of the light shielding member 20 in the stacking direction of the optical sheet 18 is arranged in parallel with the emission surface 12 a of the light guide plate 12. That is, the vicinity of the front end portion 20a of the light shielding member 20 is not only the upper surface 183b of the third sheet 183 positioned at the uppermost stage, but also by the upper edge 182e of the end edge part 182a of the second sheet 182 positioned immediately below it. The positions of the plurality of optical sheets 18 in the stacking direction are supported in a manner that matches or substantially matches, so that the vicinity of the tip 20a of the light shielding member 20 extends over a wider area and the light exit surface 12a of the light guide plate 12. In parallel, it will be stably supported.

  In addition, the first sheet 181 having the lowest number of stacked layers counted from the light exit surface 12a of the light guide plate 12 is immediately above the upper edge 181e of the end edge 181a on the light incident surface 12c side of the light guide plate 12. The position of the upper edge 182e of the edge 182a on the light incident surface 12c side of the light guide plate 12 of the second sheet 182 positioned in the position related to the stacking direction (vertical direction) of the plurality of optical sheets 18 is positioned below. ing. As a result, the light shielding member 20 extending from the light incident surface 12c side of the light guide plate 12 so as to cover the vicinity of the edge portions 181a, 182a, 183a of the plurality of optical sheets 18 of the first sheet 181 located at the lowermost stage. The inclined surface is constructed following the inclined surface. Then, the inclined surface of the light shielding member 20 is maintained from the lowermost optical sheet 181 to the position where the light shielding member 20 rides over the optical sheet 182 located immediately above the optical sheet 181 (the light shielding member 20 in FIG. 1). Reference numeral 182e is a peripheral portion). This also prevents a steep bent portion from being formed on the light shielding member 20 and ensures sufficient fixing strength of the light shielding member 20 with respect to each optical sheet 18.

Due to the above-described effects, according to the embodiment of the present invention, as shown in FIG. 5B, the optical sheet 18 is provided with tabs (for receiving the tab 120a and the tab 120a in FIG. 5A). The optical sheet 18 can be reliably positioned in the planar illumination device 10 without forming the recess 124c of the frame 124). Then, it is possible to reduce the thickness of the frame 16 in the direction of the arrow B due to the provision of the tabs on the optical sheet 18 and to promote further narrowing of the frame lighting device 10. In addition, it is possible to suppress the occurrence of uneven brightness in the planar lighting device 10 due to the provision of the tabs on the optical sheet 18.
In the embodiment of the present invention, the plurality of optical sheets stacked and disposed on the light exit surface of the light guide plate includes the first sheet 181, the second sheet 182 and the third sheet 183, and the above-described respective sheets 18 are used to It will be understood that the same effect can be obtained even if the number of optical sheets 18 increases or decreases.
Further, as shown in FIG. 4, a state before the light shielding member 20 covers the vicinity of the edge portions 181 a, 182 a, 183 a of the plurality of optical sheets 181, 182, 183 from the light incident surface 12 c side of the light guide plate 12. Then, the front and back, upper and lower discriminating means (C surface portions 181c, 182c, tabs 183d provided on the edge portions 181a, 182a, 183a of the light guide plate 12 on the light incident surface 12c side of the optical sheets 181, 182, 183. ) Is exposed without being covered by the optical sheet located in the upper stage in a mode in which the emission surface 12a of the light guide plate 12 is viewed in plan. For this reason, the light shielding member 20 of the plurality of optical sheets 181, 182, 183 in a state before covering the vicinity of the edge portions of the plurality of optical sheets 181, 182, 183 from the light incident surface 12 c side of the light guide plate 12. It will be understood that the front / back, top / bottom discrimination can be performed at a glance.

  DESCRIPTION OF SYMBOLS 10 Planar illuminating device, 12 Light-guide plate, 12a: Output surface, 12b: Main surface which opposes an output surface, 12c: Light incident surface, 12d: Inclined surface, 12e: Opposite surface, 14: Light source, 16: Frame, 18 : Optical sheet, 181: first sheet, 182: second sheet, 183: third sheet, 181a, 182a, 183a: edge part on the light incident surface side of the light guide plate, 183c: upper surface of the third sheet, 181e, 182e: upper edge of edge, 20: light shielding member, 22: sheet metal frame

Claims (8)

A light guide plate having one of a pair of opposing main surfaces as a light exit surface, a plurality of optical sheets stacked on the exit surface, a light shielding member defining an effective area of the exit surface, and the light guide plate A planar illumination device including a light source disposed opposite to a light incident surface, and a frame for housing these components,
The plurality of optical sheets are arranged such that the position of the edge portion on the light incident surface side of the light guide plate is separated from the light incident surface of the light guide plate as the optical sheet is stacked in the upper stage counted from the emission surface. The light shielding member extends from the light incident surface side of the light guide plate so as to cover the vicinity of each edge portion of the plurality of optical sheets without forming a sharp bent portion , A planar illumination device fixed to a sheet. An inclined surface is formed in a range of a predetermined width near the center portion from the light incident surface of the light exit surface of the light guide plate so that the thickness between the opposed pair of main surfaces decreases toward the center portion of the light guide plate. The range closer to the center than the inclined surface has a constant thickness,
A range of a predetermined width from an end edge portion on the light incident surface side of the light guide plate of the plurality of optical sheets is inclined following an inclined surface formed on an output surface of the light guide plate. The planar illumination device according to claim 1. A wiring board of the light source is laminated between the inclined surface of the light guide plate and an optical sheet in which a lamination step counted from the emission surface among the plurality of optical sheets is positioned at the lowest step. 3. A planar illumination device according to claim 2, wherein Among the plurality of optical sheets, the optical sheet in which the stacking stage counted from the light exit surface is positioned at the uppermost stage does not hit the inclined surface of the optical sheet positioned at the lower stage, and is a portion having a certain thickness of the light guide plate planar illumination device according to claim 2 or 3 further characterized in that it arranged parallel to the exit surface of the. Of the plurality of optical sheets, the upper surface of the optical sheet in which the stacking step counted from the light exit surface is located at the uppermost stage, and the edge of the optical sheet located immediately below the optical sheet on the light incident surface side of the light guide plate The planar illumination device according to claim 4 , wherein positions of the plurality of optical sheets in the stacking direction coincide with or substantially coincide with the upper edge. Among the plurality of optical sheets, the optical sheet in which the stacking stage counted from the exit surface is located at the lowest stage is located immediately above the upper edge of the edge on the light incident surface side of the light guide plate. of the optical sheet, the upper edge of the edge portion of the light incident surface side of the light guide plate, the position of the stacking direction of the plurality of optical sheets, claims 2, characterized in that located below 5 The surface illumination device according to any one of the above. The plurality of optical sheets are stacked on the first sheet, the first sheet having the first stacking stage counted from the exit surface of the light guide plate, the second sheet stacked on the first sheet, and the second sheet. the planar lighting device of any one of claims 1 to 6, characterized in that it comprises a third sheet. 8. The surface according to claim 1, wherein front and back and upper and lower discriminating means are provided at an edge portion of the light guide plate on a light incident surface side of the plurality of optical sheets. Illuminator.

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